use RPATH by default

[psychocoderHPC]

Add option CUDA_MEMTEST__ADD_RPATH to control if cuda_memtest is setting the rpath. The new default is that RPATH will be used but optionally allow disabling this and falling back to the old behaviori.

Using rpath's is motivated by the spack where LD_LIBRARY_PATH is not set anymore: spack/spack#28354

[PrometheusPi]

Since this is exactly the same code change as in PIConGPU, I will merge this now.